Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 344 AM EDT Tue May 15 2018 Valid 12Z Tue May 15 2018 - 12Z Thu May 17 2018 ...Strong to severe thunderstorms expected across portions of the northern Mid-Atlantic to southern New England today ... ...Heavy rain possible today from northern Kentucky to southern New Jersey, shifting to the Del-Mar-VA on Wednesday and along the Central Appalachians on Thursday... ...Heavy rain possible along the North Dakota/Minnesota border on Thursday... Scattered to widespread rain and thunderstorms will generate along a quasi-stationary front extending from the Southern Plains to Middle Mississippi Valley/Western Ohio Valley to the Northeast/Mid-Atlantic through Thursday. The eastern portion of a reinforcing front extending from the northern tip of Maine across Southeastern Canada to south-central Canada will advance southeastward into the Northeast states, merging with the stationary front tonight. The storms that move through this sector of the U.S. will have favorable conditions for becoming severe- the Storm Prediction Center has a slight risk encompassing much of the northern Mid-Atlantic and southern New England in a slight risk, with an enhanced risk covering northeast Pennsylvania to western Massachusetts/Connecticut through Wednesday morning. Additionally, heavy rain will likely set up along the frontal boundary as storms track over the same area. WPC has issued excessive rainfall outlooks for portions of the Ohio Valley, Central Appalachians, northern Mid-Atlantic and southern New England through Wednesday. The western portion of the boundary will straddle the U. S./Canadian border from the Upper Great Lakes to the Northern High Plains over the next few days. Out West, a weakening upper-level low over the Great Basin will aid in producing showers and thunderstorms over parts of the Great Basin into the Northern/Central High Plains Through Wednesday. A secondary upper-level low will move onshore over California tonight into Wednesday; which will help produce showers and thunderstorms over inland parts of the Pacific Northwest/Northern California through midweek. Another upper-level low over the Northeastern Gulf of Mexico will aid in steering moisture into the Southeast/Mid-Atlantic and the Central Gulf Coast through Wednesday. The moisture and energy will aid in producing showers and thunderstorms over parts of Florida and the Southeast that will expand into the Southern Mid-Atlantic and the Central Gulf Coast by this afternoon into Thursday. WPC has issued an excessive rainfall outlook for areas along the Central Appalachians for Thursday. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php